Finally, when I manually try the address without the www, I get redirected to the one with it.

So I’m not sure what you are seeing. Be aware that it takes time for the DNS stuff to propagate throughout the internet. Perhaps the server that you are connecting through has not gotten the new information yet.

If you put the URL manually without the “www” the redirection works.
If you click on a link that doesn’t have the “www” the redirection doesn’t work.

I’m loosing all the Google traffic that goes to my old blog. And the visitors can’t even see my message saying “I’ve moved to a new address”, sice they get redirected and then they don’t find the server.

Well, you need to talk to support about this. I am not surprised, though, that the link in the tag pages here does not resolve to a blog no longer hosted here. That is one of the problems with self-hosting: you don’t get the benefit of the global tags anymore.

Since your main wordpress address is properly resolving to the new one, you are not losing Google traffic, except for that which finds you through the global tag pages here at wordpress.COM.

I’ve moved, period. Then I payed 10 bucks for the redirection. That means that the global tags bring the user to my new domain now, and that old links referring to my old blog, go directly to the new one.

I payed 10 bucks! If everyone did like me, WordPress.com would be rich. :-)

Now the problem is:
“WHEN YOU FIND A LINK, REFERRING TO MY OLD BLOG, ON A WEBSITE (EVEN A WORDPRESS TAG, OR A GOOGLE RESULT PAGE) AND YOU CLICK ON IT, IT DOESN’T GO TO MY NEW BLOG BECAUSE WORDPRESS.COM HAVE WRITTEN MY NEW DOMAIN WITHOUT THE “WWW”.

IF YOU WRITE IT ON THE ADDRESS BAR WITHOUT THE “WWW” THE BROWSER CORRECTS IT, AND WORDPRESS HASN’T ANYTHING TO DO WITH IT.

The support already told me that they can’t add the “www” (pretty dum, huh?). But the problem is that they can’t UNDO the thing, and the visitors os my old blog (that enter because of the Google ranking) don’t find ANY page! Not even the one where I say “Hey guys, I moved”.

See the problem now? I’m loosing ALL my Google traffic. Before doint the redirection, at least 20% visited my new blog.

Thanks anyway for your time and thanks in advance to anyone that can help me.

Domain mapping is designed so that you can show your WordPress.com blog at the domain ‘ipernova.it’ instead of ‘ipernova.wordpress.com’. If you’re using it in that manner, http://www.ipernova.it will work correctly (it’ll redirect to ipernova.com, which shows your WordPress.com blog).

It looks like you’re trying to use it in the other direction, to redirect ipernova.wordpress.com to an external site. Is this correct or have I misunderstood your question?

Using domain mapping to redirect a blogaddress.wordpress.com to some other site is not supported. It’s not what domain mapping is for. It works, sometimes, but by accident not design, and it might stop altogether in future.